Fuel tank pressure

[1969CoronetR/T]

I been noticing my gas gauge going to empty and then will only take in five gallons or so of gas. I just chalked it up to the gauge malfunctioning and while it would read empty (full once I filled it up) and was close to half empty. Well, I filled it last night and then drove to my Uncle's shop to adjust the drum brakes and they needed cut as they were out of round. It purged gas in front of his shop after a half hour ride. Thought I overfilled the previous night and drove around for an hour and a half after the drums were cut. Stopped at the gas station (a common scene) and put 10 gallons in it as the gauge read empty. Drove the mile or so home and parked in the garage. An hour later I noticed a strong smell of gasoline in my house and noticed the tank was dripping gas. I took off the gas cap it gas purged a good ten seconds out of the tank and with force. Does anyone think my exhaust is heating the gas tank (I have no problems with vapor lock) or is it simply a vent tube blocked. Maybe a new gas tank is in order. Sorry about the book, but I wonder if anyone else has tis problem,
Mark

 

[WileE]

Doubt if exhaust is the culprit. Do you have a vented or non-vented gas cap ? Perhaps crud has blocked the vent, try blowing it out with air (with the gas cap off).

 

[Propwash]

Doubt if exhaust is the culprit. Do you have a vented or non-vented gas cap ? Perhaps crud has blocked the vent, try blowing it out with air (with the gas cap off).

I agree, check your venting...

 

[watermelon]

Check the connection where the inner-fill tube and gas tank meet. Make sure the inner-fill tube is inserted into the tank.

Not sure on the 69 but on a 66 the two can get separated.

 

[1969CoronetR/T]

THe gas tank and cap are fairly new and the cap appears to be non-vented. I will check the fill tubes,
Thanks,
Mark

 

[Propwash]

Check the connection where the inner-fill tube and gas tank meet. Make sure the inner-fill tube is inserted into the tank.

Not sure on the 69 but on a 66 the two can get separated.

completly different set up on 69's watermelon..There is no "inner tube". Just one that runs through the rear crossmember into the tank

 

[Cranky]

Gas stored underground is cool because the earth is cooler than the outside air. How hot has it been there lately? Gas expands a pretty good amount when it's warm vs when it's cool and shaking it up creates even more pressure and expansion. For an idea on how much pressure it makes, fill a plastic coffee can about 1/3 full and cap it then shake it. It'll usually blow the cap off and you can watch the cap actually 'dome up' just before it comes off. If you're going to top off your tank, you better be willing to drive it more than a few miles right after filling and if you fill up a car that's been on the road awhile, it'll probably over flow before you have a chance to leave the station.

 

[1969CoronetR/T]

It has been very hot in Pittsburgh lately. Eighty to Ninety degrees within the last week. I have a bad habit of filling up after I drive and then parking it in the garage. It was pouring transmission fluid out after I filled it with gas at the station. I made a trail of transmission fluid from the station to my house about a mile away. Fluid level is okay, but I ran the car pretty hard against a kid in a Itchypussie Eclipse before the transmission fluid blew out (at the station). I am having the rear main seal and front seal looked at tomorrow. Gas and transmission fluid purging in one day.....I will post my results and thanks for the help,
Mark

 

[1969CoronetR/T]

Mechanic claims the two vent tubes are open and clear so it must be the gas cap as it is not a venting gas cap. Now I have to find a place that sells vented gas caps for a 69 Coronet and see if my condition improves,
Thanks,
Mark

 

[1969CoronetR/T]

I replaced my gas cap and it seems to be working and I have not noticed any fuel purging. My old caps rubber seal was hard and not making a good seal.
Thanks to all

 

[440roadrunner]

I don't even remember where the filler is on a 69 Coronet. But if it's like the RR's, --- behind the plate-- you do NOT want a vented cap!!!

 

[1969CoronetR/T]

It is behind the license plate.

 

[440roadrunner]

It is behind the license plate.

'S what I figured. You do NOT want ANY form of vented cap on those, must be completely sealed.

The vent system on those, prior to the 70 CA vapor return and carbon can system, are very simple. Just an upside down "U" vent tube high up above the tank. It must be clear.